The present invention is an improvement on a prior control arrangement for a series or compound motor-generator in which the motor-generator has an auxiliary shunt field winding, including a feedback unit made up of at least one current-follower type DC motor that runs at high or low speed, subject to the amount of current passing through the main motor-generator armature, and an auxiliary generator, the electric energy generated by the auxiliary generator being provided to the auxiliary shunt field winding of the main motor-generator to control its output, either by assisted excitation in which the shunt field has the same polarity as the series field so that the combined field of the main motor-generator is strengthened when the main motor-generator armature current increases, or by differential excitation in which the field has a different polarity than the series field so that the combined field is reduced in response to an increase in the main motor-generator armature current.
Such a control arrangement was disclosed in U.S. patent application Ser. No. 08/032,136, filed on Mar. 17, 1993.